A typical hypodermic syringe includes a syringe barrel with a mounting collar for threadedly engaging the hub of a needle cannula. The hub and the needle cannula are connected to one another or are maintained separately from the syringe barrel until shortly prior to use. In cases where the needle is maintained separately, the medical practitioner selects an appropriate needle assembly for the procedure being carried out. The needle assembly is removed from its sterile package, and the hub of the needle assembly is threadedly engaged with the mounting collar of the syringe barrel.
Liquid pharmaceuticals and other injectable liquids are often stored in rigid containers which can be accessed using a hypodermic syringe. Some containers for liquid pharmaceuticals are plastic or glass vials with an elastomeric closure that can be penetrated by the needle of a hypodermic syringe. To access the liquid in a vial, the medical practitioner moves the plunger of the hypodermic syringe in a proximal direction to draw into the syringe barrel a volume of air substantially equal to the volume of medication that is desired. The open distal end of the needle is then urged through the elastomeric closure of the vial, and the air in the syringe barrel is injected into the vial. The distal tip of the needle and the vial engaged therewith are then pointed gravitationally upwardly. The practitioner ensures that the distal tip of the needle is covered by the medication in the vial by manipulating the needle and the vial with respect to each other. The plunger of the hypodermic syringe is then moved proximally to draw the medication through the needle and into the chamber of the syringe barrel.
After withdrawing a desires dose of medication from a vial, the medical practitioner may inject the medication into either a patient, another vial or into an injection site of an intravenous set or catheter. There is a trend toward needleless I.V. systems which do not require a pointed needle cannula to piece the injection site of an I.V. set. There are many systems that have injection sites covered by a pre-slit septum which can be accessed by a blunt cannula. Accordingly, after withdrawing medication from a vial using a sharp needle the user must remove the needle and install a blunt cannula if the medication will be used with an I.V. set. The user runs thy risk of accidental needle stick using the needle to draw the medication into the syringe and in the act of removing the needle to replace it with a blunt cannula. Also, there is the potential of contaminating the components when they are installed and removed during the filling and delivery process. Accordingly, there is a need for a device which will allow filling of a syringe from a vial having a pierceable stopper without the use of a very sharp needle and the subsequent delivery of the medication to an I.V. set through a blunt cannula without having to handle or reshield sharp needles.
Plastic vials and elastomeric closures for vials are somewhat gas permeable. Some pharmaceutical products will degrade rapidly in the presence of even small amounts of gas. Hence, these pharmaceuticals typically are stored in glass ampoules. The frangible end of a glass ampoule can be snapped off to enable access to the medication stored therein. The medical practitioner may withdraw the medication by inserting the tip of the needle on a hypodermic syringe into the medication stored in the ampoule. The plunger of the hypodermic syringe is then moved proximally to draw the liquid medication in the ampoule through the needle and into the barrel of the hypodermic syringe. The hypodermic syringe may then be withdrawn from the ampoule and used in substantially the manner described above. The ampoule typically is held with the open top gravitationally upwardly while the hypodermic syringe is being filled. This needle length required for ampoule filling may substantially exceed the length of the needle conveniently required for subsequent use for injections. Likewise, the same or similar problems exist where the medication obtained from an ampoule will be subsequently injected into an injection site having a pre-slit septum since the needle must be installed and removed from the syringe and the new blunt cannula installed. Thus, there are risks with accidental contamination and needle sticks before the properly filled syringe and blunt cannula combination are prepared.